Today's large scale computer rooms typically employ human technicians which manually load magnetic data storage media (e.g. magnetic tapes) onto computer drives. With the recent advent of computer tape cassettes (i.e., as represented by the 3480 compatible system), the space requirement for physically cataloging and storing the magnetic media has decreased (due to the decreased size of these tape cassettes as compared to the more conventional magnetic tape spools).
In my above-identified copending U.S. patent applications, there are disclosed novel robot transport systems having particular utility in the automated archiving and retrieval of computer data tape cassettes. In particular, the robot transport systems disclosed in those copending U.S. patent applications allow computer tape cassettes to be moved between a tape storage facility (where individual tape cassettes are archived) and a tape drive section (composed of individual tape drive units).
According to one aspect of the present invention, rotatable tape cassette storage carousels are provided which are especially adapted for use in the automated tape cassette archiving and retrieval systems disclosed in my above-identified copending U.S. patent applications. In general, the storage carousels of this invention include a number of vertically stacked shelf units each having a generally horizontally oriented shelf for supporting a row of tape cassettes on edge. The stacked shelf units are positioned a predetermined radial dimension from a central support shaft which is rotatably coupled to a motor-driven pedestal. Position sensors are provided in operative association with the carousel so that its particular rotational position may be sensed by appropriate supervisory controls associated with the automated tape cassette archiving and retrieval systems (e.g., to ensure that the correct shelf unit holding a preselected tape cassette is rotated into confronting relationship to a robotic manipulator associated with the robot transport system.
As may be appreciated, it is difficult (if not impossible) to eliminate entirely the possibility that a robotic manipulator will come into physical contact with the tape cassette storage unit during insertion/removal of a tape cassette into/from its particular location on the self. That is, while the controls may be designed so as to accurately guide the robotic manipulator relative to the tape storage units, it is usually inevitable that some misalignment between the tape storage unit and the robotic manipulator will occur. Thus, when attempting to insert/remove a tape cassette into/from the tape storage unit, the robotic manipulator may come into physical contact with the storage unit thereby causing mechanical shock and/or vibrations to occur. These mechanical shocks and/or vibrations may, moreover, be of such a magnitude that some of the tape cassettes may be dislodged physically from their shelf and thus tumble to the computer room floor. Needless to say, such an occurrence is extremely disruptive to an automated system since human intervention is then needed to re-shelve the dislodged computer tape cassettes. Therefore, any commercially acceptable tape cassette archiving and retrieval system must be capable of tolerating equipment "crashes" as may occur between the robotic manipulator and the tape cassette storage units.
Thus, according to a further aspect of this invention, the tape storage units are provided with means which serve to maintain the tape cassettes in their respective locations and thus minimize (if not eliminate) the possibility that the tape cassettes will become dislodged from their respective shelves in response to mechanical shocks and/or vibrations. The self units may therefore simply be provided with a raised forward lip extending the entire transverse length of the shelf to thereby serve as a stop member against which the tape cassettes abut. Alternatively (or conjunctively) means may be provided so as to, in effect, rearwardly displace the tape cassettes' centers of gravity. In this manner, the tape cassettes are encouraged to remain on the self (i.e., due to their centers of gravity being displaced away from the open front of the shelf) when the tape storage unit experiences mechanical shocks and/or vibrations.
Other aspects and advantages of this invention will become more clear after careful consideration is given to the detailed description of the preferred exemplary embodiment thereof which follows.